Male Sexual Development and the Androgenic Gland: Novel Insights through the de novo Assembled Transcriptome of the Eastern Spiny Lobster, Sagmariasus verreauxi

The Eastern spiny lobster, Sagmariasus verreauxi, is commercially important in fisheries, with growing aquaculture potential, driving an interest to better understand male sexual differentiation. Amongst the Decapoda, the androgenic gland (AG) and the insulin-like androgenic gland hormone (IAG) have a well-defined function in male sexual differentiation. However, IAG is not a sex determinant and therefore must be considered as part of a broader, integrated pathway. This work uses a transcriptomic, multi-tissue approach to provide an integrated description of male-biased expression as mediated through the AG. Transcriptomic analyses demonstrate that IAG expression is stage-and eyestalk-regulated (low in immature, high in mature and 6-times higher in hypertrophied glands), with IAG being the predominant AG-specific factor. The low expression of this key factor in immature males suggests the involvement of other tissues in male sexual differentiation. Across tissues, the gonad (87.8%) and antennal gland (73.5%) show the highest male-biased differential expression of transcripts and also express 4 sex-determination regulators, known as Dmrts, with broader expression of Sv-Sxl and Sv-TRA-2. In order to better understand male sexual differentiation, tissues other than the AG must also be considered. This research highlights the gonad and antennal gland as showing significant male-biased expression patterns, including the Sv-Dmrts.